COPYING: clarify the license

Some of the language in COPYING is potentially unclear.  For example,
there is some ambiguity in when each license option of GPL and LGPL is
allowed.  Clarify the language.

Note, this commit isn't intended to actually change the license at all.
It just clarifies what I intended.

diff --git a/COPYING b/COPYING
index c26af332a990696e75a452abbd43f278ccdcc503..5284ab3ba677dbde614ddc98136d260bf35da018 100644 (file)
--- a/COPYING
+++ b/COPYING
@@ -1,25 +1,30 @@
-Unless otherwise specified, wimlib and its associated programs, scripts,
-documentation, and other files may be redistributed and/or modified under the
-terms of the GNU General Public License; either version 3 of the License, or (at
-your option) any later version.  There is NO WARRANTY, to the extent permitted
-by law.  See the file COPYING.GPLv3 for more details.
+wimlib (meaning all programs, scripts, libraries, documentation, and other files
+that are part of the wimlib project -- not just the "libwim" library) may be
+redistributed and/or modified under the terms of the GNU General Public License;
+either version 3 of the License, or (at your option) any later version.  A copy
+of this license can be found in the file COPYING.GPLv3.
 
-Alternatively, when not prohibited by conflict with a third-party software
-license, the library portion of wimlib may be redistributed and/or modified
-under the terms of the GNU Lesser General Public License; either version 3 of
-the License, or (at your option) any later version.  There is NO WARRANTY, to
-the extent permitted by law.  See the file COPYING.LGPLv3 for more details.
+Also, when not prohibited by a third-party software license, libwim (the library
+portion of wimlib) may be redistributed and/or modified under the terms of the
+GNU Lesser General Public License; either version 3 of the License, or (at your
+option) any later version.  A copy of this license can be found in the file
+COPYING.LGPLv3.  This is offered as a "dual license", meaning that you can
+choose either this LGPLv3+ option or the above-mentioned GPLv3+ option.
 
-----------------------------------------
+In either case there is NO WARRANTY, to the extent permitted by law.
 
-NOTE! The primary reason for the GPL/LGPL "dual licensing" for the library is
-that on UNIX-like systems, wimlib can optionally be linked to the third-party
-library "libntfs-3g", which is licensed GPLv2+.  Under some interpretations of
-the GPL, this would require that wimlib be licensed under the GPL as well.
-However, a binary copy of wimlib that was compiled without libntfs-3g support
-(for example; the exception may be applicable in other situations as well)
-logically cannot be affected by libntfs-3g's license and should therefore be
-free to be redistributed under the LGPL instead of the GPL.
+--------------------------------------------------------------------------------
+
+NOTE! The reason for the "when not prohibited by a third-party software license"
+condition on the LGPL option for libwim is that libwim can optionally be linked
+to the third-party library "libntfs-3g", which is licensed under the GPL.
+Usually the GPL is interpreted in a way that means that any binary that uses a
+GPL library must be licensed under the GPL as well, not (for example) the LGPL.
+
+Therefore, if your build of libwim links to libntfs-3g, then you can't choose
+the LGPL option.  You may choose the LGPL option for Windows builds of libwim,
+since they don't link to libntfs-3g.  Likewise, you may choose the LGPL option
+for UNIX builds of libwim that were built with './configure --without-ntfs-3g'.
 
 NOTE! The file COPYING.CC0 contains a public domain dedication.  This public
 domain dedication does not apply to wimlib as a whole, but rather to individual